The poll, conducted by the MassINC Polling Group, found that while Markey is holding onto support from Democratic voters, Lynch is attracting those who are unenrolled in a party.

The poll found Markey leading Lynch, 38 percent to 31 percent. Among registered Democrats, Markey’s lead widened to 42 percent to 25 percent. However, among unenrolled voters – who can vote in either party’s primary – Lynch was ahead 38 percent to 34 percent.

“The question is do unenrolled voters actually turn out on primary day or does this turn out to be more of a base primary election, with diehard Democrats who vote every time?” said MassINC pollster Steve Koczela. “If it’s that, it looks like an advantage for Markey.”

Markey and Lynch will compete for the Democratic nomination in an April 30 primary. Markey has so far gotten support from a number of the state’s top Democratic establishment figures. Lynch is relying on support from labor and more conservative Democrats.

The Republican field has been more turbulent. So far, GOP candidates include State Rep. Daniel Winslow, former Navy SEAL Gabriel Gomez, former U.S. Attorney Michael Sullivan, former Nantucket selectman Douglas Bennett and former Ashland selectman Jon Fetherston. Former congressional candidate Sean Bielat is considering a run. All the candidates must gather 10,000 signatures by Feb. 27 in order to appear on the ballot. The general election will be held June 25.

Koczela said the Republican primary could also influence the Democratic race. If Republicans have a contested primary that attracts unenrolled voters, it could pull potential Lynch supporters away from the Democratic primary.

The poll found that the most popular and well-known political figure in the potential field of candidates is former U.S. Sen. Scott Brown, who ultimately decided not to run in the special election. Brown, who lost his Senate seat in November to Democrat Elizabeth Warren, was seen favorably by 58 percent of respondents, and unfavorably by 27 percent. Sixty two percent of respondents thought Brown should run for office again. Brown recently signed a contract as a contributor to Fox News. Most respondents (58 percent) said that would not influence their decision whether to vote for him in the future, though 26 percent said it would make them less likely to vote for him and 13 percent said it would make them more likely.

Markey and Lynch had identical favorable ratings – 29 percent – though Markey also had a slightly higher unfavorable rating, 19 percent compared to 12 percent for Lynch. Around a quarter of respondents had never heard of each of the Democratic Congressmen. But name recognition was even worse among the Republican candidates. More than half of respondents had never heard of either Winslow or Gomez, and more than a quarter of those who had heard of them did not know enough to form an impression.

“Right now name recognition is pretty low on all the candidates,” Koczela said.

The poll found that Markey and Lynch would beat an unnamed Republican candidate by double-digit margins. Both would also easily beat Winslow in a head to head matchup. MassINC did not include head to head matchups with any other Republican candidates, many of whom only announced their intentions to run this week.

The poll of 498 registered voters was conducted Feb. 11-13 and has a margin of error of 4.4 percent.